linux-kernel - Re: [PATCH v4 1/7] mfd: add syscon driver based on regmap

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Date:	Mon, 3 Sep 2012 16:02:00 +0800
From:	Dong Aisheng <b29396@...escale.com>
To:	Shawn Guo <shawn.guo@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"lrg@...com" <lrg@...com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	Zhao Richard-B20223 <B20223@...escale.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>
Subject: Re: [PATCH v4 1/7] mfd: add syscon driver based on regmap

On Mon, Sep 03, 2012 at 11:09:01AM +0800, Shawn Guo wrote:
> On Mon, Sep 03, 2012 at 10:31:03AM +0800, Dong Aisheng wrote:
> > > 
> > > I think of_node_put should be moved out from here and put into
> > > syscon_node_to_regmap and syscon_regmap_lookup_by_compatible.
> > > 
> > I guess no, if you want to move of_node_put into syscon_regmap_lookup_by_phandle,
> > then syscon_regmap_lookup_by_phandle has the same issue.
> 
> I guess not.  syscon_regmap_lookup_by_phandle itself calls of_parse_phandle,
> and that's where the refcount gets incremented, so syscon_regmap_lookup_by_phandle
> should be responsible for calling of_node_put to get the refcount decremented.
> 
Yes, the of_node_put will be done in syscon_node_to_regmap which is called by
syscon_regmap_lookup_by_phandle,
The reason why we do it is as i said in my last reply.

I think one known issue is that syscon_node_to_regmap may not be suitable to
be used by the driver who still wants to use the regmap node after calling the
syscon_node_to_regmap.
I still do not find such using case but i'm not sure whether it may exist.

Probably the safe way currently to do is just as you said:
Not put the node in syscon_node_to_regmap and let user decide.
Ok, i will update it.

Regards
Dong Aisheng

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